The present invention relates to an actuator control apparatus for correcting the operating conditions of actuators that drive an intake switching door, a mix door and mode doors in an air condition system for vehicles in correspondence to changes in the actuator operating conditions, during an adjusting operation of the actuators.
In the misalignment detection method for a numerically controlled stepping motor disclosed in Japanese Unexamined Patent Publication No. H4-294403, a signal from an origin detector is taken in for verification every time the stepping motor returns to the origin to make a decision as to whether or not the stepping motor is at the origin. More specifically, an origin hole is formed in a disk mounted at the rotating shaft of the stepping motor, an origin detector that photoelectrically detects the origin hole is provided in the vicinity of the external circumference of the disk and when an origin position command is issued, an NC device causes the stepping motor to rotate at high speed in a specific direction to start the origin positioning. In addition, a decision is made as to whether or not a light-received signal from the origin detector has been input. Then, if the light-received signal has been input, the stepping motor is caused to rotate at low speed whereas if a light-blocked signal has been input, the stepping motor is stopped. Moreover, the volume of data that corresponds to the radius of the origin hole is sent to cause the stepping motor to rotate in return, thereby implementing an origin correction, and verification is made that the light-received signal has been input again before completing the origin positioning control.
In addition, the stepping motor drive circuit disclosed in Japanese Unexamined Patent Publication No. S 60-216793, which comprises a clock circuit that generates a clock signal for controlling the rotation of the stepping motor, a distribution circuit that generates a drive signal to be applied to individual stator coils based upon the clock signal and a PWM control circuit that controls the pulse width of the drive signal so that the motor current detected at a motor current detection unit achieves a preset reference value, is further provided with a correction control circuit which controls the reference value at the PWM control circuit based upon the frequency of the clock signal to perform control of the motor current when the frequency of the clock signal becomes lower. This prevents abnormal rotation caused by an increase in the noise level and the intensified resonance due to the torque which becomes increased to an excessive degree in the vicinity of the resonance in the low speed range.
Furthermore, the four wheel steering apparatus for vehicles disclosed in Japanese Unexamined Patent Publication No. S 63-1515765, which is provided with a means for voltage detection that detects a source voltage applied to the stepping motor, performs correction in response to the output from the means for voltage detection, so that the pulse rate of the drive pulse signal for the stepping motor is increased when the voltage is at or over a specific value. Thus, since the saturation range of the drive pulse signal can be shortened, the quantity of heat generated by the stepping motor can be reduced.
However, in the method disclosed in Japanese Unexamined Patent Publication No. H4-294403, it is necessary to provide a disk and an origin detector at the drive shaft in order to detect and correct misalignment of the drive shaft, and this will go against the general requirements for space saving and a reduction in the number of parts when adopted for driving automotive parts in particular.
In addition, when operating conditions for the actuators change greatly and the members being driven by the actuator are constituted of resin or the like to achieve light weight, as in automobiles, it will result in a significant degree of deformation of the members, and this gives rise to a problem in that a reset cannot be implemented to the correct original set positions. If the actuators are driven at high torque in order to solve this problem, a new problem arises in that operating noise increases.
In the case of the stepping motor drive circuit disclosed in Japanese Unexamined Patent Publication No. S60-216793, on the other hand, since the drive torque is further reduced when the source voltage falls, a problem arises in that a member driven by an actuator cannot reach a specific position. In addition, if the source voltage rises, the member driven by the actuator is driven past the target position, causing a high level of noise and misalignment from the origin position. Problems such as these which are related to changes in the source voltage cannot be solved through the method for source voltage correction disclosed in Japanese Unexamined Patent Publication No.S63-1515765.